ci(appsec): fix ddwaf circular import

[mabdinur]

Fix the following CI failures: https://gitlab.ddbuild.io/DataDog/apm-reliability/dd-trace-py/-/jobs/774636553

Reproduction:

from ddtrace.appsec._metrics import _set_waf_init_metric

• ddtrace/appsec/_metrics defines _set_waf_init_metric
• ddtrace/appsec/_metrics imports ddtrace.appsec._proccessors
• ddtrace.appsec._proccessors imports _set_waf_init_metric
• Boom: Circular import

The fix here is to avoid importing ddwaf from ddtrace.appsec._processor in ddtrace.appsec._metrics. Instead we can import ddwaf directly from ddtrace.appsec._ddwaf.

This issue does not occur if the ddtrace.appsec._processor module is imported before ddtrace.appsec._metrics. This is why we do not see this error in most of our appsec tests. However the order of imports is not guaranteed by the slots check. This explains the flakiness in this job.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

ddtrace/appsec/_metrics.py                                              @DataDog/asm-python

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: munir/fix-ddwaf-circular-import
Commit report: 8b1c81e
Test service: dd-trace-py

✅ 0 Failed, 130 Passed, 1468 Skipped, 4m 28.11s Total duration (35m 41.38s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-21 19:35:29

Comparing candidate commit 8b1c81e in PR branch munir/fix-ddwaf-circular-import with baseline commit f198341 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 362 metrics, 2 unstable metrics.